Space
Shuttle Basics

The space shuttle
is the world's first reusable spacecraft, and the first spacecraft
in history that can carry large satellites both to and from orbit.
The shuttle launches like a rocket, maneuvers in Earth orbit like
a spacecraft and lands like an airplane. Each of the three space
shuttle orbiters now in operation -- Discovery, Atlantis and Endeavour
-- is designed to fly at least 100 missions. So far, altogether
they have flown a combined total of slightly more than one-fourth
of that.

Columbia was
the first space shuttle orbiter to be delivered to NASA's Kennedy
Space Center, Fla., in March 1979. Columbia and the STS-107 crew
were lost Feb. 1, 2003, during re-entry. The orbiter Challenger
was delivered to KSC in July 1982 and was destroyed in an explosion
during ascent in January 1986. Discovery was delivered in November
1983. Atlantis was delivered in April 1985. Endeavour was built
as a replacement following the Challenger accident and was delivered
to Florida in May 1991. An early space shuttle orbiter, the Enterprise,
never flew in space but was used for approach and landing tests
at the Dryden Flight Research Center and several launch pad studies
in the late 1970s.

The space
shuttle consists of three major components: the orbiter which houses
the crew; a large external fuel tank that holds fuel for the main
engines; and two solid rocket boosters which provide most of the
shuttle's lift during the first two minutes of flight. All of the
components are reused except for the external fuel tank, which burns
up in the atmosphere after each launch.

The
longest the shuttle has stayed in orbit on any single mission is
17.5 days on mission STS-80 in November 1996. Normally, missions
may be planned for anywhere from five to 16 days in duration. The
smallest crew ever to fly on the shuttle numbered two people on
the first few missions. The largest crew numbered eight people.
Normally, crews may range in size from five to seven people. The
shuttle is designed to reach orbits ranging from about 185 kilometers
to 643 kilometers (115 statute miles to 400 statute miles) high.

The shuttle
has the most reliable launch record of any rocket now in operation.
Since 1981, it has boosted more than 1.36 million kilograms (3 million
pounds) of cargo into orbit. More than than 600 crew members have
flown on its missions. Although it has been in operation for more
than 20 years, the shuttle has continually evolved and is significantly
different today than when it first was launched. NASA has made literally
thousands of major and minor modifications to the original design
that have made it safer, more reliable and more capable today than
ever before.

Since
1992 alone, NASA has made engine and system improvements that are
estimated to have tripled the safety of flying the space shuttle,
and the number of problems experienced while a space shuttle is
in flight has decreased by 70 percent. During the same period, the
cost of operating the shuttle has decreased by one and a quarter
billion dollars annually — a reduction of more than 40 percent.
At the same time, because of weight reductions and other improvements,
the cargo the shuttle can carry has increased by 7.3 metric tons
(8 tons.)

NASA is prepared
to continue flying the shuttle for at least the next decade and
plans to continue to improve the shuttle during the next five years,
with goals of increasing its safety by improving the highest-risk
components. NASA will also be working to correct the problems identified
by the Columbia Accident Investigation Board during the investigation
of the STS-107 accident.

In managing
and operating the space shuttle, NASA holds the safety of the crew
as its highest priority.